In continuation of our past research interests, we intend to investigate a number of connected problems on the relation between the structure and function of pancreatic deoxyribonuclease (DNase). This research promises to lead to a substantial clarification of the mechanism of DNase action and also should extend the usefulness of the enzyme as a tool in research on nucleic acid structure and on the genetic role of DNA. Major problems to be investigated include the following: 1. Chemical modification of the active site, including the use of bifunctional alkylating agents and pseudo-substrates. The amino acid sequence about the active site residues also will be studied. 2. Physical studies on metal binding to DNase, including a study with ORD, CD, and UV spectra of the change in protein structure which accompanies reversible metal binding. Rate and stability constants for the binding of several metals will be obtained. 3. The role of metals in DNase action, including an investigation of the different catalytic properties of native DNase and the metal-DNase complex. The inhibition of DNase by Hg ion and the stabilization of the enzyme by Ca ion and Mn ion against inactivation by chymotrypsin or trypsin also will be studied. 4. The specificity of DNase, including an investigation of the relative specificity of DNase for single- and double-stranded DNA. The relative specificity of native DNase and metallo-DNase in the hydrolysis of different homopolymers also will be compared.